[CODE HEALTH] Move sdk_builder.cc builders into anonymous namespace

[thc1006]

Summary

Wraps the 10 file-local builder classes in
sdk/src/configuration/sdk_builder.cc within an anonymous namespace,
clearing the 10 misc-use-internal-linkage warnings clang-tidy reports
on this file. Second production-code PR of the misc-use-internal-linkage
campaign, after #4121 (registry.cc).

Changes

• sdk/src/configuration/sdk_builder.cc: insert namespace { after the
  using common::WildcardMatch; declaration at line 189 and
  } // namespace before the first SdkBuilder:: member function
  definition at line 750. Wrap covers ResourceAttributeValueSetter,
  SamplerBuilder, SpanProcessorBuilder, SpanExporterBuilder,
  MetricReaderBuilder, PushMetricExporterBuilder,
  PullMetricExporterBuilder, AggregationConfigBuilder,
  LogRecordProcessorBuilder, and LogRecordExporterBuilder. The 10
  classes use inline methods only and are not referenced from any other
  translation unit (verified by repository-wide grep).
• .github/workflows/clang-tidy.yaml: abiv1 366 -> 356 (-10),
  abiv2 372 -> 362 (-10).
• CHANGELOG.md: one bullet under [Unreleased].

Linkage rationale

SdkBuilder:: member function definitions remain at namespace scope
outside the anonymous namespace, because as members of class SdkBuilder
they must keep external linkage to satisfy ODR. The anonymous namespace
contents are reachable from the member function bodies via the implicit
using-directive that hoists anonymous namespace symbols into the
enclosing configuration namespace. This is the same structure used in
#4121.

Test plan

• Local build of opentelemetry_configuration and 7 yaml tests
  (-DWITH_CONFIGURATION=ON, 119/119 ninja steps)
• yaml_propagator_test passes 9/9
• yaml_test passes 50/50
• yaml_trace_test passes 38/38 (exercises Sampler / SpanProcessor /
  SpanExporter builders)
• yaml_metrics_test passes 32/32 (exercises MetricReader /
  PushMetricExporter / PullMetricExporter / AggregationConfig builders)
• yaml_logs_test passes 20/20 (exercises LogRecordProcessor /
  LogRecordExporter builders)
• yaml_resource_test passes 13/13 (exercises ResourceAttributeValueSetter)
• yaml_distribution_test passes 3/3
• clang-format --dry-run --Werror clean on the modified file
• DCO signed off

Part of #2053

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.00%. Comparing base (5533a30) to head (19c7879).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4122   +/-   ##
=======================================
  Coverage   82.00%   82.00%           
=======================================
  Files         385      385           
  Lines       16031    16031           
=======================================
  Hits        13144    13144           
  Misses       2887     2887           

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